Multiply and let rip, perhaps (6)
I believe the answer is:
Here is my best explanation:
'multiply' is the definition.
(tripling is a kind of multiplying)
'let rip perhaps' is the subsidiary indication.
'perhaps' indicates anagramming the letters.
'letrip' anagrammed gives 'triple'.
'and' is the link.
(Other definitions for triple that I've seen before include "Three times", "Consisting of three", "Multiply by three", "three times", "make score sixty?", "Threefold, treble", "Increase threefold", "In three parts", "Let rip with a threesome" and "make much longer".)